A control apparatus (100) for a gas sensor (10) which includes a cell (2) composed of a solid electrolyte body and a pair of electrodes provided thereon. The control apparatus includes voltage application means (70) for applying a single pulse voltage to the cell over a constant energization time T; first-output-value obtaining means 70 for obtaining a first output value Vri1 from the cell when a first time t1 shorter than the constant energization time has elapsed; second-output-value obtaining means (70) for obtaining a second output value Vri2 from the cell when a second time t2 shorter than the constant energization time but longer than the first time has elapsed; and deterioration-degree detection means 70 for detecting the degree of deterioration of the cell on the basis of a difference ΔVri between the second output value and the first output value.
Legal claims defining the scope of protection, as filed with the USPTO.
1. A control apparatus for a gas sensor which includes a cell composed of an oxygen-ion-conductive solid electrolyte body and a pair of electrodes provided thereon and which generates a sensor output corresponding to concentration of a specific gas, the control apparatus comprising: a voltage applicator that applies a single pulse voltage to the cell over a constant energization time; a first-output-value obtainer that obtains a first output value from the cell when a first time shorter than the constant energization time has elapsed after a start of application of the single pulse voltage; a second-output-value obtainer that obtains a second output value from the cell when a second time shorter than the constant energization time but longer than the first time has elapsed after the start of application of the single pulse voltage; and a deterioration-degree detector that detects a degree of deterioration of the cell based on a difference between the second output value and the first output value.
2. The control apparatus for a gas sensor according to claim 1 , wherein the second time is longer than two times the first time.
3. The control apparatus for a gas sensor according to claim 1 , wherein the voltage applicator again applies the single pulse voltage after a waiting time equal to or longer than 10 times the constant energization time has elapsed after the previous application of the single pulse voltage.
4. The control apparatus for a gas sensor according to claim 1 , wherein the gas sensor is placed in a passage through which exhaust gas from an internal combustion engine flows; the control apparatus comprises a determiner that determines an air-fuel ratio of the exhaust gas based on the sensor output; and the deterioration-degree detector detects the degree of deterioration when the air-fuel ratio determined by the determiner is a specific air-fuel ratio.
5. The control apparatus for a gas sensor according to claim 4 , wherein the determiner determines, based on the sensor output, whether the air-fuel ratio of the exhaust gas is on a rich side or a lean side; and the deterioration-degree detector detects the degree of deterioration when the specific air-fuel ratio determined by the determiner is an air-fuel ratio on the rich side.
6. The control apparatus for a gas sensor according to claim 1 , wherein the gas sensor includes a heater for heating the cell; and the control apparatus further comprises a heater controller that controls an amount of electric current supplied to the heater such that the cell assumes a target impedance, and a changer that changes the target impedance based on the degree of deterioration detected by the deterioration-degree detector.
7. A method for controlling a gas sensor which includes a cell composed of an oxygen-ion-conductive solid electrolyte body and a pair of electrodes provided thereon and which generates a sensor output corresponding to concentration of a specific gas, the method comprising: applying a single pulse voltage to the cell over a constant energization time; obtaining a first output value from the cell when a first time shorter than the constant energization time has elapsed after a start of application of the single pulse voltage; obtaining a second output value from the cell when a second time shorter than the constant energization time but longer than the first time has elapsed after the start of application of the single pulse voltage; and detecting a degree of deterioration of the cell based on a difference between the second output value and the first output value.
8. The method according to claim 7 , wherein the second time is longer than two times the first time.
9. The method according to claim 7 , further comprising again applying the single pulse voltage after a waiting time equal to or longer than 10 times the constant energization time has elapsed after the previous application of the single pulse voltage.
10. The method according to claim 7 , wherein the gas sensor is placed in a passage through which exhaust gas from an internal combustion engine flows, and the method further comprising: determining an air-fuel ratio of the exhaust gas based on the sensor output; and detecting the degree of deterioration when the determined air-fuel ratio is a specific air-fuel ratio.
11. The method according to claim 10 , further comprising: determining, based on the sensor output, whether the air-fuel ratio of the exhaust gas is on a rich side or a lean side; and detecting the degree of deterioration when the specific air-fuel ratio determined by the determiner is an air-fuel ratio on the rich side.
12. The method according to claim 7 , wherein the gas sensor includes a heater for heating the cell, and the method further comprises: controlling an amount of electric current supplied to the heater such that the cell assumes a target impedance; and changing the target impedance based on the degree of deterioration detected by the deterioration-degree detector.
Cooperative Patent Classification codes for this invention. Click any code to explore related patents in that topic.
November 28, 2011
May 13, 2014
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